The wars of this century have involved the use of massive numbers of high explosive munitions. Shells, bombs, and landmines all function in substantially the same way. A high explosive charge fills the munition housing. This high explosive charge is characterized by its relative stability and insensitivity to shock, handling, and temperature changes. This enables the munitions to be safely handled and transported without the risk of accidental detonation. A small booster or initiator of a more sensitive explosive is typically provided to detonate the high explosive. A fuze is then provided to detonate the booster when a specific event occurs. For example, a bomb fuze may detonate the booster after a specific pre-selected time has elapsed after the bomb has been dropped. Similarly, an artillery fuze may detonate a shell on impact after firing, or at a predetermined height above ground. And the fuze in a landmine will detonate the booster when a predetermined amount of pressure is sensed.
Most munitions function as intended and explode when they are supposed to. However, some munitions malfunction and do not explode. Such munitions are not safe, and often remain buried beneath the surface of the ground, presenting a significant hazard which can render an area so dangerous that it is no longer habitable. Almost eighty years after the end of World War I, there are still areas in France which remain fenced-off due to the danger of unexploded munitions. The greater hazard, of course, occurs in the areas which are still inhabited. Farmers in France still plow up unexploded ordnance; some of them are injured or killed in the process. The same problems exist in other areas of the world where conflicts have raged, from Germany to Africa, and from Kuwait to Bosnia or Vietnam.
Conventional methods of removing buried, unexploded munitions are time consuming and often dangerous. For example, conventional methods often involve the location of the buried, unexploded munitions by an individual who inserts a probe into the soil, until a solid object is encountered. The solid object is excavated, and if found to be an unexploded munition, it can be remotely detonated using a conventional high explosive charge, such as a block of TNT or C-4, placed onto or next to the munition. This method can be risky when the buried munitions contain magnetic fuzes, when the personnel clearing the area are not careful, and when anti-personnel mines are present.
Other conventional methods include remotely detonating explosive charges above the surface of the area thought to contain mines, in an attempt to detonate them, and propelling a heavy weight or roller over the area thought to contain mines (for example, in front of an armored vehicle), to detonate the mines. The primary disadvantages for these methods are (1) it can be dangerous since some mine fuzes can be set to count occurrences, and detonate on the second or subsequent occurrence (i.e., the pressure exerted by the heavy weight is sufficient to count as an occurrence, but doesn't detonate the mine; the pressure exerted by the armored vehicle pushing the weight is also sufficient to count as an occurrence, and will detonate the mine if the fuze is set to detonate on the second occurrence); (2) this method is not very likely to detonate munitions which are buried more deeply than mines (more than 1-2 feet below the surface), or munitions which do not use pressure fuzes.
Accordingly, the need exists for a safe method of detecting buried ordnance so that steps can be taken to remove the hazard by physically removing the ordnance, or by detonating it remotely.